MIAMI — Attorneys representing potentially thousands of Guatemalans who were affected by U.S. syphilis experiments decades ago said Tuesday they will sue top federal health officials unless a system is created out of court to settle claims by the victims or their survivors.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The legal move comes after revelations last year that U.S. scientists studying the effects of penicillin in the 1940s deliberately infected about 700 Guatemalan prisoners, mental patients, soldiers and even orphans — some as young as 6, according to the lawyers. None were informed or gave consent.

The American team convinced officials at orphanages and prisons to cooperate by giving them other supplies such as refrigerators and difficult-to-get medications for malaria and epilepsy. Sometimes, individual subjects were paid with cigarettes and, in the case of prisoners, infected prostitutes were used to expose them to the disease, according to court documents.

Two law firms said in a letter to Attorney General Eric Holder that the lawsuit, which could become a class-action, will be filed in federal court in Washington unless President Barack Obama's administration responds positively to the settlement offer by Friday.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"We have decided to create one opportunity to see if we can settle the issues presented in this tragic situation without involving the judicial process," said the letter from attorneys Andres Alonso and Terrence Collingsworth.

A Justice Department spokesman declined to comment. Last October, Secretary of State Hillary Rodham Clinton and Health and Human Services Secretary Kathleen Sebelius called the experiments "reprehensible" and issued a public apology. Obama also apologized to Guatemalan President Alvaro Colom in a phone call and created a special bioethics panel to look into international medical studies, the White House said.

The administration's apologetic tone led the Guatemalans' attorneys to seek the unusual out-of-court settlement before a lawsuit is filed. They want the U.S. to waive any sovereign immunity defenses to block the Guatemalan claims or, as an alternative, they want a claims process similar to those set up in the Gulf of Mexico oil spill and the Sept. 11 terror attacks.

"This is to encourage the administration to take the next step," said Piper Hendricks, an attorney with Fort Lauderdale-based Conrad & Scherer LLP who is working on the case.

The Guatemalan experiments ran from 1946 to 1948 and were funded by the National Institutes of Health. Their existence was hidden for decades, until Wellesley College medical historian Susan Reverby uncovered the records in 2009.

The U.S. has been involved in numerous other infamous medical studies on human subjects. The most notorious was the Tuskegee syphilis research on 600 black men in Alabama who were studied without being offered any treatment. The physician involved in that study, Dr. John Cutler, was also involved in the Guatemalan research.

The attorneys said Guatemala was chosen because it would be easier to escape ethical scrutiny there.

"This decision to move to Guatemala was part of a deliberate plan to continue the Tuskegee testing offshore, where it would not be subject to the same level of oversight as in the United States," their draft lawsuit says.

It's unclear how many potential plaintiffs could be part of the class, which would include not only those directly involved in the research but also their relatives and survivors. The lawsuit, if filed, seeks an unspecified amount of damages for violations of people's rights including "cruel, inhuman and degrading treatment" and medical experimentation on humans without consent.

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